Certain fluoro-containing nitro-acetal compounds

ABSTRACT

1. AS COMPOSITIONS OF MATTER, THE COMPOUNDS HAVING THE FORMULA: WHEREIN R IS A RADICAL SELECTED FROM THE GROUP CONSISTING OF HYDROGEN AND LOWER ALKYL; R1 IS A RADICAL SELECTED FROM THE GROUP CONSISTING OF HYDROGEN AND LOWER ALKYL; AND A IS A LOWER ALKYLENE RADICAL.   R-C(-R1)(-O-A-C(-NO2)2-F)2

United States Patent Oifice 3,629,338 Patented Dec. 21, 1971 3,629,338CERTAIN FLUQRO-CONTAINING NITRO-ACETAL COMPOUNDS Fred E. Martin, Azusa,Calif assignor to Aerojet- General Corporation, Azusa, Calif. NoDrawing. Filed July 6, 1064, Ser. No. 381,293 Int. Cl. C07c 43/30 US.Cl. 260-615 A 8 Claims This invention relates to novel fluoro-containingnitroacetal compounds and methods for their preparation. Morespecifically, this invention relates to an improved method of preparingfiuoro-containing nitroacetal compounds.

It is an object of this invention to prepare novel chemical compounds. Afurther object of this invention is to provide a novel class of acetalswhich are superior solid rocket plasticizers due to their improvedcompatibility, stability and energy value. It is another object of thisinvention to provide a new process for preparing chemical compounds.Still another object of this invention is the provision of a group ofacetals possessed of enhanced impact and ballistic properties. These andother objects of the invention will be apparent from the detaileddescription which follows.

The nitroacetals of this invention have the following L l loz wherein Ris a hydrogen or an alkyl radical; R is a hydrogen or an alkyl radical;and A is an alkylene radical. Preferably, the alkyl radicals in theforegoing formula are the lower members of the series, i.e., memberscontaining from 1 to about 8 carbon atoms. Most preferably, as can beseen from the examples appearing hereinafter, R and R are hydrogen oralkyl from 1 to 4 carbon atoms; and A is alkylene of l to 4 carbons.

The novel method of this invention comprises reacting an aldehyde or aketone with fluoro-dinitroalcohol in accordance with the generalreaction scheme set forth below:

wherein R, R and A are as defined above.

It will be apparent that a great number and variety of compounds withinthe scope of this invention can be prepared by reacting an aldehyde orketone with a fluoro dinitroalcohol in accordance with the methoddescribed herein. Examples of aldehydes and ketones suitable asreactants for my novel methods are: isobutyraldehyde, isopentanaldehyde,Z-methyl butyraldehyde, Z-methyl pentanaldehyde, S-methylpentanaldehyde, 2-ethyl enanthaldehyde, Z-isopropyl enanathaldehyde,methyl isopropyl ketone, methyl isobutyl ketone, ethyl isobutyl ketone,ethyl hexylketone, ethyl isohexyl ketone, diisopropyl ketone, dibutylketone, diethyl ketone, and methyl octyl ketone. Examples offluoro-dinitroalcohols suitable as reactants for the method of thisinvention are: 3-fluoro-3,3-dinitropropanol;S-difiuoro-5,5-dinitro-n-pentanol; 4-fluoro-4,4- dinitro-n-butanol; andZ-fluoro-2,2-dinitroethanol.

It is within the scope of my invention to form the aldehyde or ketonestarting material for the above reaction scheme in situ. Thus, a polymerwhich depolymerizes to yield an appropriate aldehyde or ketone can beadded to the system along with a suitable depolymerization catalyst. Forexample, paraldehyde, a trimer of acetaldehyde, can be depolymerized insitu to furnish acetaldehyde for my novel reaction. Likewise,paraformaldehyde, a polymer of formaldehyde, can be added along with adepolymerization catalyst which causes it to break down and yieldformaldehyde in situ. Good yields of the desired acetals are alsoobtained when the formaldehyde is generated in situ from s-trioxane.Catalysts particularly adaptable for this purpose are catalysts such assulfuric acid, boron trifluoride, (BF ferric chloride, ptoluene sulfonicacid, m-benzene disulfonic acid, Zinc chloride, HCl, HF, borontrifluoride complexes etc.

The reaction temperature is not critical to the operability of my novelmethod, the only significantelfect of an increase or decrease intemperature being a corresponding increase or decrease in reaction rate.While reaction temperature is not critical, it is preferred, for reasonsof economy of operation and convenience, to employ temperatures withinthe range from 20 C. to about 50 C. in the practice of this invention.

The process may be carried out at any convenient pressure, normally from0.1 to about 100 atmospheres. Normally, the reaction is carried out atordinary atmospheric pressure. The reactants may be employed in varyingratios. However, usually the aldehyde and fluorodinitroalcohol are usedin about stoichiometric amounts. The catalysts employed in the reactionare preferably present in an effective catalytic amount of from about0.1 percent to about 20 percent by weight, based on the total weight ofreactants.

The reaction of this invention is preferably conducted in asubstantially inert solvent. Any organic solvent known to those skilledin the art, such as benzene, toluene, chloroform, carbon tetrachloride,methylene chloride, ethylene dichloride, etc., is suitable as a mediumfor the reaction of this invention. Although I prefer to employ anorganic solvent as a reaction medium, it is within the scope of myinvention to conduct the reaction in any other suitable liquidcompatible with the system. For example, an excess of a reactant, suchas 3-fluoro-3,3-dinitropropanol, or a liquid catalyst, suoh as sulfuricacid, which may include small amounts of water, can be so employed.

It is preferable to conduct the reaction of this invention in thepresence of a catalyst, especially in the presence of an acid esterification catalyst. The acid esterification catalysts are dehydratingagents which take up the water as it is formed during the reaction. Thecatalysts mentioned above as suitable for the in situ formation ofaldehydes and ketones are likewise suitable for the primary reaction ofour invention. Consequently, where in situ depolymerization is to beeffected, the same material can be employed to accomplish this and tocatalyze my novel reaction. In addition, compounds generally capable offorming alcoholates such as, for example, calcium chloride are suitablecatalysts for the reaction of this invention. However, for the highestyields, it has been found that some catalysts are uniquely suited foruse in certain reactions. Specifically, it has been found thatconcentrated sulfuric acid to 99 percent by weight) gives superioryields of formaldehyde, bis-(2-fluoro-2,2-dinitroethyl) acetal.

The fluoro-tlinitroalcohol reactants, such as 2-fiuoro-2,2-dinitro-ethanol, are preferably prepared by the fluorination of thecorresponding dinitroalcohol or salt thereof according to the methoddescribed in assignees copending US. patent application Ser. No.214,169, filed July 27, 1962, now US. Pat. No. 3,387,044.

It will be apparent that a great number and variation of acetals withinthe scope of the invention can be prepared by reacting appropriatestarting materials according to the method taught therein. Mixtures ofthe reactants of my novel method can be employed in the practice of myinvention.

area-ass It will be apparent that the no\el nitroacctals of thisinvention are either acetals or itetals. depending on the nature of theR and R radicals. in the generic formula. However. all of my novelcompositions are generically referred to and identified herein as.icctals in accordance with the normal practice employed in theliterature. This practice is recogni/ed and followed by ChemicalAbstracts as noted in Sec. 209 of the nomenclature pamphlet entitled TheNaming and Indexing of Chemical Compounds by Chemical Abstracts (1961).available at the Office of Chemical Abstracts, the Ohio StateUniversity. Columbus. Ohio.

To contribute to a better understanding of this in vention. thefollowing examples are presented. It should be understood. however. thatthese examples are presented merely as a means of illustration and thatthe invention is not limited to the particular embodiments andconditions described therein.

EXAMPLE I Preparation of formaldehyde. bisl lluot'o dinitrocthyl) acetalA 15.3 g. portion of 2.2-dimtro-Z-fiuorocthanol in 30.6 ml. of ethylenechloride was charged into a l-ml.. three necked flask equipped with amagnetic stirrer. thermometer and a drying tube. The reaction mixturewas stirred and maintained at 20 to 25 C. while 16.8 ml. of 96 percentsulfuric acid was added during minutes. A 1.5 g. portion of 95 percentparaformaldehyde was added in one portion and the mixture w as stirredduring 1.68 hours. The sulfuric acid layer was removed and the organiclayer was washed 4 times \HIl'l [5 ml. portions of 1.25 N NaOH. then 4times with ml. portions of distilled water. The organic layer wasfiltered. then stripped of volatiles at 50 C. and 5 mm. Hg. Weight ofproduct: 1 1.7 g.. 1.4395. Infrared curve confirmed disappearance of thehydroxyl group and the formation of the ether linkage.

AnuIysis.-Calc'd for C H O N F tpercent): C, 18.76: H. 1.89; F, 11.67.Found (percent): C. l9.l5'. H, 1.98; F, 10.96.

EXAMPLE ll Preparation of methyl-n-butyl ketone. bis- 5-fiuoro-5,5-dinitro-l pentyll acetal 5-lluoro-5.5-dinitro l pentanol 0.5mole) dissolved in about 300 ml. ethylene chloride is charged into aflask equipped with a stirrer. thermometer. and a drying tube. Thereaction mixture is stirred and maintained at to C. while about 60 ml.of concentrated sulfuric acid is added during 15 minutes. Thenmethyln-butyl ketone (0.25 mole) is added and the mixture is stirredabout 2.0 hours. The sulfuric acid layer is removed and the organiclayer is washed 4 times with 60 ml. portions of 1.25 N NaOH. then 4times with 60 ml. portions of distilled water. The organic portion isfiltered and stripped of volatiles. Infrared curve confirmeddisappearance of the hydroxyl group and the formation of the etherlinkage.

EXAMPLE Ill Preparation of propionaldehyde. blsd 3-l'luoro-3,3-dinitropropyl) acetal sulfuric acid layer is removed and the organiclayer is washed 4 times with 100 ml. portions of l.25 N NaOH. then 4times with I00 ml. portions of distilled water. The organic portion isfiltered and stripped of volatiles. lt'opioualdehydc. his-t 3-tluoro t-.liuitiopiop \li is obtained in good yield.

tcttal 4 EXAMPLE lV Preparation of acetaldehyde, bis-(4-fluoro-4,4-dinitrobutyl) acetal A one mole portion of4-fiuoro-4,4-dinitro-l-butanol in 30.6 ml. of methylene chloride wascharged into a flask equipped with a stirrer and thermometer. Thereaction mixture was stirred and maintained at 20 to 25 C. While 300 ml.of concentrated sulfuric acid was added during about 50 minutes. Aone-half mole portion of acetaldehyde was added in one portion and themixture was stirred during about 3.0 hours. The sulfuric acid layer wasremoved and the organic layer was washed 4 times with ml. portions of1.25 N NaOH, then 4 times with 100 ml. portions of distilled water. Theorganic portion is filtered. and stripped of volatiles. Infrared curveconfirmed disappearance of the hydroxyl group and the formation of theether linkage. The product recovered represented a high yield ofacetaldehyde, bis-(4-fiuoro-4,4-dinitrobutyl) acetal.

EXAMPLE V Preparation of acetaldehyde, bis-(2-fluoro-2,2 dinitroethyl)acetal A 0.2 mole portion of 2-fluoro-2,2-dinitroethanol in about 30 ml.of ethylene chloride was charged into a flask equipped with a stirrerand thermometer. The reaction mixture was stirred and maintained at 20to 25 C. while about 12 ml. of boron triiluoride was added during 5minutes. A 0.1 mole portion of acetaldehyde was added in one portion andthe mixture was stirred during about 1.5 hours. The organic material Waswashed 4 times with 25 ml. portions of 1.25 N NaOH, then 4 times with 25ml. portions of distilled water. The organic portion is filtered andstripped of volatiles. Infrared curve confirmed disappearance of thehydroxyl group and the formation of the ether linkage. A good yield ofacetaldehyde, bis-(2- fiuoro-lldinitroethyl) acetal was obtained.

The fiuoro-containing nitroacetals prepared by the novel method of thisinvention are excellent plasticizers for use in the preparation ofpolyurethane binders for high energy solid rocket propellants such asthose disclosed in assignees copending US. patent application Ser. No.829,- 180, filed July 20, 1959, now US. Pat. No. 3,245,849. The acetalsare also suitable as plasticizers for nitrocellulose and nitropolymerssuch as the nitro-substituted polyurethane polymers disclosed inassignees copending US. patent application Ser. No. 728,491, filed Apr.14, 1958,

now abandoned. The plasticizers prepared as taught here in contribute tothe energy of propellants in which they are incorporated, because oftheir high nitro content, while possessing good chemical and thermalstability. Hence, they are superior to the commercial plasticizers WhlChcontain no nitro groups and are. accordingly, substantiallynonenergetic. In addition, the fluoro-containing nitroacetals preparedby the method of this invention are compatible with those polyurethanesystems in which the monomers contain gem-dinitro or nitraza groups,with which systems most plasticizers commercially available at presentare incompatible.

In utilizing my fluoro-containing nitroacetals as plasticizers fornitropolymer polymerization, the nitropolymers can be polymerized in thepresence of the plasticizer or the plasticizer can be mixed into thenitropolymer after polymerization thereof. The plasticizers areincorporated into the nitropolymers in amounts preferably within therange from about 10 percent to about 40 percent by weight of thecomposition. When utilizing the acetals as plasticizers forpolyurethanes which contain no nitro groups. such as the polyurethanebinders for the solid propellants of the above-mentioned copending US.patent application. Ser. No, 829.l80, the techniques of incorporatingthe plasticizer into the binder is essentially the same as that usedwith nitropolymers. The plasticizers are preferably incorporated in thepropellants in amounts up to about 15 percent by weight thereof.

As explained in copending applications Ser. Nos. 728,- 491, nowabandoned, and 829,180, now U.S. Pat. No. 3,245,849, thenitro-substituted polyurethanes of the former and the polyurethanepropellants of the latter can be used as a primary propulsion source inrocket-propelled vehicles, and can also be used as a propellant forartillery missiles. When used as the primary propulsion source forrocket vehicles, they can be conveniently ignited by a conventionaliguiter, as for example, the igniter disclosed in assignees copendingU.S. Pat. No. 3,000,312. The propellant is preferably cast in tubularform and restricted in the conventional manner with a relatively inertresin, such as a non-nitrated polyurethane foam or a polyester resin,and placed inside a chamber having one end open and leading into aconventional venturi rocket nozzle. Upon ignition, large quantities ofgases are produced and exhausted through the nozzle creating propulsionforce.

The preferred plasticizers for use in solid propellants areformaldehyde, bis-(2-fluoro-2,2dinitroethyl) acetal, and acetaldehyde,bis-(2-fluoro-2,2-dinitroethyl) acetal. It has been found that thesecompounds blend most readily with the other propellant ingredients.

The nitroacetals of Formula I are unique among acetal compounds in thatthey possess the ideal combination of properties for a propellantplasticizer, namely, high energy and excellent compatibility with thepolyurethane binders, and good chemical and thermal stability.

Having described the invention, it is intended that it be limited onlyby the lawful scope of the appended claims.

I claim: 1. As compositions of matter, the compounds having the whereinR is a radical selected from the group consisting of hydrogen and loweralkyl; R is a radical selected from the group consisting of hydrogen andlower alkyl; and A is a lower alkylene radical.

2. As compositions of matter, the compounds having wherein R is aradical selected from the group consisting of hydrogen and lower alkyl,and A is a lower alkylene radical.

3. As compositions of matter, the compounds having the formula:

R1 N03 3 O A 3 F] L 150, wherein R is lower alkyl radical, R is a loweralkyl radical, and A is a lower alkylene radical.

4. As compositions of matter, the compounds having the formula:

H HO;

wherein A is a lower alkylene radical.

5. As compositions of matter, the compounds having the formula:

r n RCH O-A-o-F] 2 wherein R is a lower alkyl radical, and A is a loweralkylene radical.

6. As a composition of matter, the compounds having wherein A is a loweralkylene radical.

7. As a composition of matter, formaldehyde, bis-(2-fiuoro-2,2-dinitroethyl) acetal.

8. As a composition of matter, acetaldehyde, bis-(2-fluoro-2,2-dinitroethyl) acetal.

References Cited UNITED STATES PATENTS LELAND A. SEBASTIAN, PrimaryExaminer U.S. Cl. X.R. 14919, 88

1. AS COMPOSITIONS OF MATTER, THE COMPOUNDS HAVING THE FORMULA: